The present invention generally relates to orthodontic arch wires, and more particularly to an arch wire formed of a plurality of metallic strands in the form of a tightly wound elongated coil.
The following definitions apply to the specification and claims. "Stiffness" is the resistance of a material to bending or deformation. "Flexibility" is the ability of a material to bend or deform. "Plastic deformation" is a permanent change in the shape of a material. Once plastic deformation takes place, the removal of forces which caused the change in shape does not result in a return of the material to its original shape. The "elastic limit" of a material is the maximum load or deformation which can be applied to a material before plastic or permanent deformation takes place. "Resiliency" is the tendency of a flexed material to spring back to its original configuration on the removal of the flexing forces. "Working Range" is the range of deformation of a material where it retains its resiliency, up to a maximum deformation which can be sustained by a material without exceeding the elastic limit and becoming permanently deformed with loss of resiliency.
Orthodontic procedures usually require the placement of a tooth band and bracket upon respective maloccluded teeth and the employment of an arch wire for interconnecting the bands or brackets relative to one another so that a force is transmitted from one band to the next and thereby to the teeth upon which the bands are mounted. Today, the orthodontist is offered a wide variety of arch wires. The known arch wires vary both in size and material. An ideal arch wire must be flexible, but must have sufficient stiffness or body over long lengths so that it can serve as a relatively fixed anchoring or reference point to which other orthodontic devices can be connected. The flexibility, of course, is required so that the arch wire can be bent into the shape of an arch in the mouth. It is also desirable that the arch wire have a resiliency and sufficient range over short and long lengths in order to permit the application of local biasing forces to the teeth.
Coiled arch wires consisting of a single metallic strand in the form of a tightly wound helix are known from my earlier U.S. Pat. Nos. 3,861,042, issued Jan. 21, 1975 and 3,878,609, issued Apr. 22, 1975. Coiled orthodontic arch wires made of a single coiled strand are also disclosed in my copending U.S. Application Ser. No. 535,687, filed Dec. 3, 1974.
The object of the present invention is to provide an orthodontic arch wire fabricated of a plurality of strands which are wound in the form of an elongated coiled arch wire, and which would have generally similar if not better characteristics than my earlier coiled arch wires which are formed of a single tightly wound strand.